Recently, a surveying apparatus structured so that a target can be automatically collimated based on an image obtained from an imaging device has also started to be used. As such a surveying apparatus, one as disclosed in the following Patent Document 1 has been known. This is shown in FIG. 11 and FIG. 12.
The surveying apparatus includes, as shown in FIG. 11, a telescope composed of an object lens 1, a dichroic mirror 2, a condenser lens 3, and a solid-state image pickup device 4 on a collimation axis (optical axis) O, and a light that has penetrated through the object lens 1, dichroic mirror 2, and condenser lens 3 is focused on the solid-state image pick device 4.
In addition, the surveying apparatus has a light emitting unit 6, and a modulated light emitted by the light emitting unit 6 is sent along the collimation axis O through a condenser lens 7, a triangular mirror 5, dichroic mirror 2, and object lens 1. The modulated light that has been sent along the collimation axis O returns along the collimation axis O as a result of being reflected on a target prism (hereinafter, simply described as a target) disposed at a point of measurement, penetrates through the object lens 1, dichroic mirror 2, and condenser lens 3, and is made incident onto the solid-state image pickup device 4. A part of the modulated light is reflected on the dichroic mirror 2 and triangular mirror 5 and is made incident into a light receiving unit 8 through a condenser lens 9.
In the surveying apparatus, a phase difference between the modulated light emitted by the light emitting unit 6 and the modulated light made incident into the light receiving unit 8 is determined by an unillustrated phase meter, and based on the phase difference, a distance to the target is calculated by an unillustrated arithmetic control unit. At this time, a horizontal angle as well as a vertical angle of the telescope (a collimation axis) are measured by an unillustrated horizontal measuring unit (horizontal encoder) and vertical angle measuring unit (vertical encoder).
Meanwhile, when measuring the distance and angles, the target must be collimated so that this is accurately positioned on the collimation axis O. This collimation is automatically carried out as follows.
First, the telescope is turned to a target 11, and in terms of an image including the target 11 as shown in FIG. 12(A), a lit image when the light emitting unit 6 has been made to emit light and an unlit image when the light emitting unit 6 has been turned off are obtained by the solid-state image pickup device 4. Then, by the unillustrated arithmetic control unit, a difference between both images is determined. From the difference between both images, as shown in FIG. 12(B), an image of only the target 11 is obtained. This allows determining a horizontal deviation H and a vertical deviation V of the target 11 from the center of a screen indicating a collimation axis O direction. Then, by rotating the telescope by an unillustrated horizontal drive unit (horizontal servo motor) and vertical drive unit (vertical servo motor) until the horizontal deviation H and vertical deviation V become zero, the target 11 can be automatically collimated.
Although the foregoing collimation is carried out when the telescope stands still, automatic collimation can be carried out even when the telescope is rotating. The angle of rotation of the telescope is determined by counting the number of output pulses from the unillustrated horizontal angle measuring unit and vertical angle measuring unit. For example, if a difference in angle of the telescope between, while the surveying apparatus is horizontally rotating, when the light emitting unit 6 is made to emit light to obtain a lit image and when the light emitting unit 6 is turned off to obtain an unlit image is determined, a shift amount X (angle difference) between the lit image and unlit image can be easily calculated as shown in FIG. 12(C). When the shift amount X between the images has been determined, by determining a difference between both images by shifting either the lit image or unlit image by the shift amount X, the horizontal deviation H and vertical deviation V are easily determined, and the target 11 can be automatically collimated.
As such, since the surveying apparatus disclosed in the following Patent Document 1 is capable of carrying out automatic collimation irrespective of whether the telescope is rotating or at a stand still, automatic collimation can be easily carried out at any time.
[Patent Document 1] Japanese Patent No. 3621123